This invention relates generally to the method of coupling the output shaft of an actuator to a valve. Actuators are used to open and close a valve. This invention applies in particular to quarter-turn butterfly valves.
A butterfly valve is a flow control device which incorporates a rotational disk to control the flowing media in a pipe. It generally consists of a body, liner, shaft and disk assembly for insertion between a pair of spaced flanges in a fluid passageway more commonly known as a pipe and having the ability to seal off the flow completely at one extreme of its rotation and the ability to allow maximum flow through the pipe at the other extreme of its rotation and to provide some measure of reduced flow capacity at any point in between these two extremities.
An actuator is a control device mounted on a valve which causes the disk of a butterfly valve to rotate. Actuators are either manual or automatic and can be operated by hand, electronics, pneumatics, hydraulics, or springs. The proper actuator for a given valve application must be selected due to torque requirements imposed by the valve application, the means of operation available or practical at the valve location, and cost.
An actuator can be either manual or automatic. An actuator is the device which mechanically causes disk to rotate. As noted above, actuators can be powered by different power sources; however, for illustration purposes of this invention, a pneumatic actuator is used as an example (FIG. 1).
The rack and pinion mechanism simply consists of a length of linear gearing (rack) and pinion gear, which serves as the rotary output shaft. The gear rack is fitted to or machined directly into an arm on the face of the piston. As the piston strokes, the gear rack engages and drives the pinion at a dimension from the center of rotary output, which is the radius of the pinion shaft (FIG. 1). This produces torque. The stroking length of the piston is limited, so that the actuator produces output torque over 90 degrees (1/4 turn) of rotation.
The gear rack contacts the pinion at a point that is a constant dimension from the center of rotation; therefore, the torque output throughout rotation is constant. When the pinion shaft is connected directly to the shaft of a butterfly valve, this provides the most direct connection without the use of brackets and couplings.
To date there are several manufacturers of actuators for direct mount to their own manufacture of butterfly valves. In each case the manufacturer of the actuator must machine an output shaft that is fitted to their own butterfly valve. If a valve manufacturer does not manufacture its own actuator for direct mounting to its own butterfly valve, the valve manufacturer must use an actuator manufactured by another manufacturer and must adapt this actuator to his valve with the use of brackets and couplings.
Quarter turn valves are actuated with either manual or automatic actuators. Automatic quarter turn actuators are commonly pneumatic or electric. When valves are operated by actuators, the actuator usually has to be mounted to the top of the valve using a bracket as a connecting member. The valve shaft is then connected by a coupling to the actuator shaft. The valve is then opened or closed by transferring the torque from the actuator to the valve through the rotary motion of the actuator shaft through the coupling.
In this configuration the actuator shaft has to be of the same general configuration as the valve shaft i.e. if the valve shaft is of a parallel flat configuration the actuator shaft must be of the same female configuration to accept the valve shaft.
To date, each butterfly valve manufacturer presenting a direct mounting capability of its actuator with its valve has to have an actuator of sufficient dimension and output shaft configuration to mount only to and drive only its own manufacture of valves.
The concept of mounting actuators to quarter turn valves has been known in the art for many years. Some of the difficulties encountered with actuators having standard drive dimensions is that a specialty coupling has to be designed and manufactured each time an actuator is mounted or applied to any quarter or half turn valve.
When a special request is made for a connection configuration that is not within the fabricators manufacturing standard, a new shaft for the actuator has to be designed, manufactured, and tested, in order to comply with the requirement This type of request has to be handled as a special project each time, which is costly and time consuming, and often interrupts and delays standard production.